The method of rigorous coupled-wave analysis (RCWA) is developed to analyze the diffraction properties of acoustic parity-time-symmetric gratings. Asymmetric diffraction can be generated in these gratings, and the +1st order transmitted wave is suppressed completely at the diffraction vanishing point (DVP). The influence factors of the modulation ratio of the DVP, including the modulation amplitude and modulation approach, are systematically discussed using the method of RCWA. Two-beam diffraction with Bragg incident angle is studied in detail. The results show that the modulation ratio of the DVP changes with the modulation amplitude differently for different modulation approaches. The attenuation or enhancement of the sound energy depends on the sign of incident angle and the modulation ratio.

中文翻译：

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用严格的耦合波分析研究奇偶时间对称光栅的不对称衍射。

提出了一种严格的耦合波分析方法（RCWA）来分析声奇偶时间对称光栅的衍射特性。在这些光栅中可以产生不对称衍射，并且在衍射消失点（DVP）处完全抑制了+1阶透射波。利用RCWA方法系统地讨论了DVP调制比的影响因素，包括调制幅度和调制方式。详细研究了布拉格入射角的双光束衍射。结果表明，对于不同的调制方式，DVP的调制比随调制幅度的变化而不同。声能的衰减或增强取决于入射角和调制率的符号。